Air leakage from distribution ductwork wastes energy by increasing fan power and discarding conditioned air. Assuming about 5% duct leakage, approximately 380 gigawatt-hours of fan power are lost on duct leakage per year. Duct leakage also results in significant heating and cooling energy penalties when conditioned air leakage is discarded from the envelope in exhaust or relief air systems. The recent development of a novel, patented sealing process (Aeroseal) makes it possible to tightly seal ductwork in retrofit applications as it requires significantly less access than traditional methods.

This project characterized duct leakage in several types of Minnesota commercial and institutional buildings, completed retrofit duct sealing on a subset of duct systems, and estimated the energy savings and cost effectiveness of retrofit sealing measures. The project then analyzed the results to develop screening criteria that displace cost-prohibitive leakage measurements and tested the criteria in a short pilot program to identify cost-effective duct sealing opportunities.

Main research conclusions:

Measured leakage was lower than expected, but still represents an opportunity of about 460 gigawatt-hours of electric savings and 2,900 million cubic feet of gas savings per year.

Researchers estimate 15% of commercial and institutional buildings will yield cost-effective opportunities (about a seven year payback over a long lifetime).

The primary energy savings are from natural gas and the primary cost savings are from electricity.

Research results recommend immediately incorporating measures into existing programs such as commercial auditing, recommissioning and turn-key savings. In addition outreach should be conducted to inform and educate vendors on the benefits of retrofit duct sealing measures.

This project was supported in part by a grant from the Minnesota Department of Commerce, Division of Energy Resources through the Conservation Applied Research and Development (CARD) program. The project was co-funded by CEE in support of its nonprofit mission to advance research, knowledge dissemination, and program design in the field of energy efficiency.